KUMAMOTO -- Following a magnitude-6.5 earthquake that struck here on the night of April 14, 120 perceptible aftershocks were recorded as of 9 a.m. the next day.
The earthquake, rating a 7 on Japan's 7-point seismic intensity scale, hit at about 9:26 p.m. on April 14. The aftershocks have included an upper-6 temblor on the Japanese scale.
According to the Japan Meteorological Agency (JMA), the Kumamoto quake has registered the third most magnitude-3.5-plus aftershocks of any inland or coastal temblor after the 1995 Great Hanshin Earthquake, behind only the Niigata Chuetsu Earthquake of 2004 and the Iwate-Miyagi inland earthquake of 2008. The comparison was made from the five and a half hours after each quake.
Aftershocks are continuing. Gen Aoki, head of the JMA's earthquake and tsunami monitoring division, warns that aftershocks of up to a lower-6 on the Japanese scale may occur for around the next week.
"Please do not approach dangerous places like partially fallen buildings," he cautioned.
Furthermore, the JMA announced that for the first time it had detected long-seismic wave tremors rating at the highest level of a four-level scale when the upper-6 aftershock occurred at around 12:03 a.m. on April 15. The JMA began releasing these long-seismic wave tremor ratings in March 2013. A level four on the scale means that on the upper floors of a skyscraper "one cannot stand, and must crawl to move."
The earthquake may have loosened the ground in the area, and mudslides are likely if there is heavy rain. Because of this, the JMA on April 15 temporarily lowered its standard for releasing heavy rain warnings by from around 70 to 80 percent for municipalities where an upper-5 or higher quake was recorded.
To check on earthquake damage and on quake observation points, the JMA has sent a team composed of members from its headquarters' earthquakes and volcanoes department, its Fukuoka Regional Headquarters and elsewhere to areas where tremor levels between a 7 and a lower-6 on the Japanese scale have been detected.